Shaft sinking adjacent to the largest high grade uranium deposit in the world at Cigar Lake, Sask., should re-commence this week.
Regina-based mining contractors Thysson Mining Construction of Canada are back on the site, according to Cigar Lake Mining general manager George Peoples.
Cigar Lake Mining is a wholly- owned operating company established by the joint venture owners, Saskatchewan Mining Development (48.75%), Cogema Canada (32.625%), Idemitsu Uranium Exploration Canada (12.875%), Corona Grand (3.75%) and Korea Electric Power (2%).
The contractor left the site early this spring to allow another contractor to erect the headframe and carry out other site preparation work. That work is now complete.
The circular shaft, 16-ft in diameter was driven through 35 m of overburden and 6 m of bedrock late last winter. The target depth is 510 m, which should be reached sometime late next year or early 1990. To facilitate test-mining, the company then plans to drift out from the shaft on two levels, one above (at a depth of 420 m in sandstone) and one below the orebody (at 470 m in the crystalline basement rocks).
The 150,000-tonne deposit, averaging 14% U3O8, contains 385 million lb of U3O8. Thickness varies from one to 20 m with an average of about 7 m.
By driving all development headings in waste rock above and below the deposit, miners will be shielded from very high levels of gamma radiation from the deposit.
The company plans to use proven raisebore machines, widely used in underground mining operations, to mine the clay-hosted ore from bottom to top. Raisebore machines would be used to ream a small- diameter hole to, perhaps, 3 m. The operator of the machine will work from a remote location in the drift above, again to avoid direct contact with the ore.
Prior to excavating each hole, the pitchblende and clay ore, which has minimal cohesion and low strength, will either be grouted or frozen. Then, after each hole is reamed it will be plugged with backfill.
Mill construction should start in 1992 and should be in operation in 1993.
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